Silane forming size and glass fiber strands threated therewith for resin reinforcement



Feb. 2, 1965 G. E. EILERMAN 3,168,389

SILANE FORMING SIZE AND GLASS FIBER STRANDS TREATED THEREWITH FDR RESINREINFORCEMENT Filed Dec. 28, 1960 INVENTOR.

GEORGE E. EILEBMAN WWW ya United States Patent i 3,168,389 SILANEFGRMING SIZE AND GLASS FIBER STRANDS TREATED THEREWITH FOR RESINREINFURCEMENT George E. Eilerman, Perrysviile, Pa., assignor toPittsburgh Plate Glass Company, Pittsburgh, Pa., :1 corporation ofPennsylvania Filed Dec. 28, 1960, Ser. No. 79,031

'13 Claims. (Cl. 65-3) The present invention relates to a glass fibertreatment and it has particular relation-to a size for treating glassfibers which are to be used in various forms as a reinforcement forresins. This application is a continuationin part of my applicationSerial No. 825,432, filed July 7, 1959, now abandoned.

A glass fiber strand is composed of a multitude of fine glass filamentswhich are formed by being drawn at a high rate of speed from moltencones of glass located at the tips of small orifices in a bushing suchas shown in U.S. Patent No. 2,133,238. During formation, the filamentsare coated while moving at a speed of the order of 5,000 to 20,000 feetper minute with a size which contains a binder to give the strandintegrity for workability, i.e., for twisting, plying and weaving. Ifthe strand does not have proper integrity, fuzzing occurs during theseoperations and eventually the strand breaks. The size also contains alubricant for the filaments to prevent destruction of the strand byabrasion of the individual filaments against each other or against fiberhandling equipment.

It is common practice to use glass fiber strands and glass fiber clothas a reinforcement for resins. For such use, the glass fiber are coatedwith a coupling agent or finish material which makes the surface of theglass fibers hydrophobic and compatible with the particular resins withwhich they are to be employed. These coupling agents greatly increasethe dry and wet flexural strength of the glass fiber-resin laminate.

A number of silane and siloxane materials have been found to be usefulas coupling agents. For example, vinyl and allyl halo, alkoxy, amino oracyloxy silanes, their hydrolysis products and polymers of thehydrolysis products are uitable for such use. Some of the silanes aredisclosed in U.S. Patents Nos. 2,563,228; 2,688,006; 2,688,007;2,723,211; 2,742,378; 2,754,237; 2,776,910 and 2,799,598.

When the glass fibers are used in the form of strand, i.e., roving orchopped strand or twisted strand, for resin reinforcement, the couplingagent is usually combined with the size and applied with the size to thefibers during their attenuation and forming. The size employed isusually an aqueous dispersion of (1) a film-forming, synthetic resinlatex made by aqueous emulsion polymerization of an ethylenic monomer,for example, polyvinyl acetate latex, and (2) a textile lubricant orsoftener. Roving is formed by combining a number of strands in parallelform and winding the strands on a tubular support in a manner such thatthe combined strands may be unwound and used to form woven roving orchopped strands. made according to conventional textile twistingtechniques by removing the strand from the forming package and windingit on a twister bobbin. It is therefore necessary that the strand havegood integrity and resistance to Twisted strand (single end on a bobbin)is' 3,168,389 Patented Feb. 2, 1955 fuzzing during the steps employed tomake the twisted strand or roving and fabricate them into forms suitablefor useas a resin reinforcement.

When roving is woven to form a roving cloth for resin reinforcement, itis necessary that the roving have a certain degree of hardness. Theroving should be hard and flexible, but not brittle. If the roving istoo soft, it fuzzes in the heddles. When this occurs, the weavingoperation must be interrupted to remove the fuzz. If the fuzz is notremoved, it causes the woven roving to have loops and holes in it andotherwise be non-uniform.

Ordinarily, when it is desired to make a strand or roving harder forweaving purposes, the procedure is to increase the amount of binder inthe size. There is a limit to the amount of binder which can be appliedin the size during the formation of the strand because too much binderon the strandwill render the strand diificult to remove from the formingpackage. It has been found that the use of the maximum allowable amountof binder, such as polyvinyl acetate latex, in a silane-containing sizedoes not render the strand or roving sufficiently hard for some weavingprocedures. It is therefore an object of this invention to provide asilane size for application to strands, during their formation to enablethe production of a relatively hard roving. The term hard roving means aroving which has good strand integrity and which feels hard to the touchas contrasted to a soft roving which feels soft to the touch.

A further object of this invention is to produce a single type of hardroving which can be used as a reinforcement for different type ofresins. Vinyl and allyl silanes have been used to treat glass fiberswhich are to be combined with styrenated, polyester resins. It isbelieved by some persons that during polymerization of the resin in situwith the glass fibers, there is a chemical reaction between theunsaturated groups in the resin and the unsaturated groups in the silanecoating on the fibers. It is desired that a treatment be provided forglass fiber roving which will render the roving capable of providing anincreased flexural strength to glass fiber resin laminates in generaland not just to laminates of specific resins. For example, it is desiredthat a roving be provided which is equally useful as a reinforcement forstyrenated polyester resins and epoxy resins. It is obvious that such aversatile roving will reduce the storage and inventory problems of bothmanufacturers and users of the roving.

An additional object of the invention is to provide glass fiber rovingwhich has been treated with a size containing an alkenyl silane, such asvinyltriacetoxy silane, with good wet out properties. It is desirable inthe formation of glass fiber laminates that the resin completelyimpregnate the strand and wet the surfaces of the fibers as quickly aspossible in order to reduce the time required to make the laminates aswell as to provide a laminate with maximum possible strength.

It is a further object of this invention to provide a glass fiber strandwhich is treated with a size containing a coupling agent and which canbe twisted, plied and woven into cloth for use as a resin reinforcementwithout requiring heat cleaning and finishing of the cloth prior to suchuse as isnow required. 7

These and other objects of the invention are accomplished by treatingglass fiber strands during their forma tion with a size containing abinder, a lubricant or softener,

- 30 minutes before being added to the latex.

water is ,then addedto make 250 gallons of sizing solution. The sizingsolution as thus prepared has a pH of about an alkenyl acyloxy silanesuch as vinyltriacetoxy silane and an amino-alkylalkoxy silane such' asgamma-aminopropyl triethoxy silane.

The alkenyl acyloxy silanes contemplated for use in the presentinvention are illustrated by the following structural formula:

(R1) ..si(0 412) 4-n wherein R is an alkenyl radical selected from thegroup consisting of vinyl and allyl radicals, R is H or an alkyl orsubstituted .alkylradical containing'l to carbon atoms audit is a wholenumber from 1 to 3, preferably 1. Typical examples of the alkenylacyloxy silanes which are usable in accordance with the presentinvention are listed below: I

R2 wherein R may be H, an alkyl radical containing 1 to 5 carbon atomsor H[NHCH -CH x being 1 to 5, R

may be H or an alkyl radical containing 1 to 5 carbon atoms, R3 and R4are alkyl radicals preferably containing 1 to 5 carbon atoms, and n is awhole number from 1 to 3, preferably 1. Typical examples of theamino-alkyl alkoxy silaneinclude gamma-amino-propyl triethoxysilane andsimilar silanes produced in the manner shown in US. Patent No.2,832,754.

A typical example of the size is as follows.

Example I Ingredient: ,Parts by weight Aqueousdispersion of polyvinylacetate latex (55% by weight of solids) 129.1 Pelargonic acid amidesolubilizedin water with acetic acid (KL-185a) 5.0 Vinyltriacetoxysilane1 1.0 Gamma-amino-propyl triethoxysilane 5.5 Water 1942 Two hundredfifty gallons of the glass fiber size can be made by dispersing thepolyvinyl acetate latex in about 80 gallons of water in a mixing tank.The textile softener RL-185a is added to about 70 gallons of watermaintained at a temperature of about 130 to 160 F. and thoroughly mixedtherein. This mixture is then added to the aqueous dispersion of thelatex. The vinyltriacetoxysilane and the gamma-amino-propyltriethoxysilane are mixed separately with equal amounts of cold water,added to each other and then added immediately, say for example withinten minutes, to the mixing tank. It has been found that the improvementin Wet-out properties is not obtained if the silane mixture is allowedto stand for too long a time, i.e. Sutficient 4.3 tov 4.7 anda solidcontent of about 3.5 to 4.1 percent by weight;

It is desirable to add the silanes together in an aqueous a small amountof plasticizer in it.

gamma-amino-propyl triethoxysilane is alkaline and if it is added by.itself, it will tend to precipitate some of the polyvinyl acetate latexfrom the dispersion.

The sizing solution is applied to the individual fibers during theirformation in the manner illustrated in the drawing. The sizing solutionis applied to the individual form a strand, by means of a rollerapplicator 18 which is composed of a rotating roller19 partiallysubmerged in the sizing solution 20 contained in a reservoir 22. Such anapplicator is shown in more detail in US. Patent No. 2,728,972. Thefibers are grouped into a strand by a graphite guide 24and wound arounda forming tube 26 rotatingat approximate 7500 r.p.m. to produce a strandtravel of approximately 12,000 to 15,000 feet per minute. Other methodsof applying the size to the strand of glass fibers, such as a padapplicator, may be employed and the strand may be formed by means otherthan Winding on' the forming tube, such as by means of a pair ofrotating wheel pullers which direct the strand into a suitablecollecting device. The glass fiber strands wound on the forming tube 26are then dried. This may be done by heating them at a temperature andfor a length of time sufiicient to remove substantially all of thewater, for example at about 275 F. for 8 hours; This drying causes thesilanes to fix themselves to the glass surface and to produce the degreeof strand integrity and hardness required for forming the strandginto awoven cloth or woven roving. The solids content of size on the strandaverages about 0.5 to 2.0 percent by weight, preferably about 0.75percent by weight.

The glass fiber size can be made by using other filmforming, glass fiberbinders in place of thepolyvinyl acetate latex. .These binders arelatices, i.e., aqueous dispersions of synthetic resins made by aqueousemulsion polymerization of 'ethylenic monomers, such as the variousacrylates which are esters of acrylic and methacrylic acid and analiphatic alcohol having 1 to 6 carbon atoms including for example,methyl methacrylate and methyl acrylate. Other ethylenically unsaturatedmonomers can also be employed to form homopolymeric and copolymericlatices within the purview of this invention, e.g., vinyl chloride,styrene, acrylonitri'le, chlorovinyl acetate, butadiene, vinylidenechloride and various copolymers of the above monomers such as'butadiene-styrene, butadieneacrylonitrile, vinyl chloride-vinyl acetatecopolymers and like materials which can be employed in latex form inaqueous dispersions as binders for glass fiber strands. These latices.generally have an average particle size of 0.1 toS microns.

A plasticizer may be'used in the size with latices which tend to depositas brittle or discontinuous films although ordinarily aplasticizer isnot used for it tends to soften the roving. For example, a plasticizermay be used with latices of polyvinyl acetate, polyvinyl chloride, thepoly- .acrylates and polystyrene, Whereas the plasticizer is generallynot used with butadiene-styrene latex. Frequently the latex as purchasedfrom the manufacturer will have The plasticizer may be any knownplasticizer for the various latices such as dibutyl" phthalate,tricresyl phosphate, dioctyl phthalate, dii'soo'cty'l phthalate andother esters which are conventional- -ly used'as plasticizers.Approximately 1 to 5 percent by weight of the latex on a solid basis isemployed in the size. Approximately 0.5 to 5 percent by weight ofplasticizer based upon the weight of the solid latex may be employed.Larger amounts may be employed with polyvinyl chloride, polystyrene andpolyvinylidene chloride latices if needed for proper-film forming.

The size contains about 0.3 to 2 percent by weight of aualkenyl acyloxysilane such as vinyltriacetoxysilane and about 0.1 to Zpercent by weightof an amino-alkyl alkoxyl silane such as gamma-.amino-propyltriethoxysilane. The amount of vinyltriacetoxysilane is usuallyl to 4times the amount of gamma-amino-propyl triethoxysilane in the size.Greater than 2 percent by weight of each of the silanes can be used, butlarger amounts do not materially increase the flexur-al strengthcharacteristics of the resin laminates. It'is preferred that no morethan about 2 percent by weight of the gamma-amino-propyl triethoxysilanebe employed because adequate hardness is obtained by such amount. Whereexceptionally hard roving is desired, however, greater amounts of thegamma-aminopropyl triethoxysilane may be employed.

The textile softener for use in the present invention is acationic-active, acid solubilized, fatty acid amide. A suitable materialis manufactured by the Arnold Hoffman Company under the trade numberRiv-185a. It is an anhydrous material which is a deep reddish, amber,viscous liquid .at room temperature. It is water dispersible and has apH of 8.9 to 9.4 in a one percent by weight aqueous dispersion. Othercommercially available acid solubilized, fatty acid amides are useful astextile softeners imidazolines which may be formed by causing fattyacids to react with polyalkylene polyamines under conditions whichproduce ring closure. The reaction of .tetraethylene pentamine withstearic .acid is exemplary of such reaction. These imidazolines aredescribed more fully in U.S. Patent No. 2,200,815. Other suitableimidazolines are described in U.S. Patents Nos. 2,267,965; 2,268,273 and2,355,837.

The size may contain a wetting agent. The wetting agent is preferablycationic or non-ionic and it may also serve as an additional lubricant.Any material which is conventionally known'to be useful as such and willre duce the surface tension of the sizing solution so that it is about 5to 35 dynes per square centimeter can be used. Such materials includecetyl or stearyl monoamine hydrochloride or acetate, dodecyl amine,hexadecyl amine and secondary and tertiary derivatives of the same, forexample, dodecyl methyl amine and salts thereof. Alkyl quaternaryammonium compounds such as trimethyl stearyl or cetyl ammonium bromides.and chlorides and generally any of the amine compounds that dissociatein water systems to provide a positive radical containing a group ofmore than 8 and preferably 12 or more carbon atoms may be used. Otherexamples of suitable wetting agents are polyoxyethylene derivatives of asorbitol fatty acid ester such as polyoxyethylene sorbitan monostearateor polyoxyethy-lene sorbitan trioleate. The amount of such wetting agentemployed generally ranges from about 0.01 to 1 percent by weight of theaqueous sizing solution.

The total solids content of the sizing solution is about 2 to 5.5percent by weight of the solution. In all events the amounts of thevarious ingredients should not exceed that amount which will cause theviscosity of the solution tobe greater than about 100 centipoises at C.Solutions having a viscosity of greater than 100 centipoises at 20 C.are very difficult to apply to glass fiber strands during theirformation Without breaking the strand. It is preferred that theviscosity of the size be between 1 and 20 centipoises at 20 C. for bestresults. The pH of the solution may vary from about 3 to 8 dependingupon the sensitivity of the latex to precipitate from the dispersion.The more sensitive the latex is to precipitation, the higher the pH ofthe solution. It is desired that 6 the sizing solution have a pH of 4 to5 when polyvinyl acetate is the latex.

Further examples of the sizing solutions which may be employed in thepresent invention are listed below.

' This sizing solution is made in the same manner as that in Example Iwith the melamine formaldehyde resin being added as the final ingredientjust prior to the final addition of the water. It has been found thatthe addition of about 0.3 to 2 percent by weight of melamineformaldehyde to the size serves several purposes. The

strand which is sized with the solution of Example H is whiter in colorthan the strand sized with the solution of Example I. The melamineformaldehyde resin provides this improved color and does so whileslightly decreasing the hardness of the strand thus formed. This isimportant for the addition of the gamma-amino-propyl triethoxysilane tothe size increases the hardness of the strand as well as making it morecompatible with epoxy resins. The melamine formaldehyde resin istherefore useful to control the hardness ofthe strand thus produced.

The melamine formaldehyde resin in" the size improves the abrasionresistance of the strand and permits twisting of the strand according toconventional textile twisting and plying techniques without unduebreakage of filaments. The twisted strand (yarn) can be woven into clothand combined with a resin without requiring heat cleaning and finishingof the cloth as has been required in the past. Prior to this inventionglass fiber strands which have been twisted into yarn have almostexclusively been sized with a starch-vegetable oil containing size topermit twisting. The starch-oil size had to be burned off after the yarnwas woven into cloth and the cloth had to be treated with a silane orchrome finish in order to make the cloth compatible with organicresinous materials.

The size of Example II is applied to the strand in the same manner asdescribed above with respect to the size of Example I and the treatedstrand is dried as described above and fabricated into various textileproducts, such as twisted strand, cloth, chopped strand, chopped strandmat, roving and woven roving. Further examples of the sizing solutionswhich may be applied to glass fibers as described above are as follows.

' 7 Example 111 Ingredient: 1 Parts by weight Butadiene styrene latex(48% by weight solids) 129.1 Vinyltriacetoxysilane 11.0Gamma-amino-propyl triethoxysilane 5.5 Tetraethylene pentamine amide ofstearic acid solubilized in water with meth'acrylic acid 5 .0 Water 1942Example IV Ingredient: Parts by weight Polymethyl methacrylate latex(40% by weight of solids) 129.1 Vinyltriacetoxysilane l 1.0Gamma-amino-propyl triethoxysilane 5.5 Textile softener (anhydrous, acidsolubilized fatty acid amide) 5.0 Water 1942 The strandswhich have beensized with the solutions are fabricated as described above provideincreased flexural strengths to resins reinforced with the strand.'Glass fiber cloth woven from 60 end roving treated as described inExample H was laminated with a styrenated polyester resin. The cloth waswoven on an Axminster loom according to a 1 to 1 pattern resulting in60' ends 'of 204 filamentE type glass strand (140s) in both the warp andfill. Four plies of the cloth were individually saturated with the resinand then stacked upon each other to insure proper nesting. The resin wasa 'polymerizable mixture of a styrenated polyester containing about 2percent by weight of methyl ethyl ketone peroxide and 3 percentbyweight'cobalt; The assembly was cured for several hours at roomtemperature and atmospheric pressure. The resulting'laminate had about60 percent by weight of glass and dry flexural strength of 67,700 poundsper square inch.. After a 2-hour immersion in boiling water the flexuralstrength of the laminate was 60,100 pounds per square inch. 7

The invention is particularly useful when the glass fibers are who usedas reinforcement for low pressure thermosetting type resins, forexample, unsaturated polyester-ethylenic resins such .as shown in US.PatentNo. 2,676,947, granted to Parker. These resins. are inter- Ipolymersof, (A) a polyester of a dihydric alcohol such as ethyleneglycol, propylene glycol, 1,3-butylene glycol, diethylene glycol,dipropylene glycol and higher polymers of alkylene 'glycols, and analpha, beta ethylenic, dicarboxylic acid such as maleic or fumaric acidwith (B) other polymerizable ethylenic monomers such as styrene, vinylacetate, vinyl toluene, allyl esters including allyl acetate, allylsuccinate, diallyl phthalate, diallyl cyanurate, triallyl cyanurate,dichloro styrene, etc.

The invention is also useful when the glass fibers are to be laminatedwith other resinous or plastic materials such as polyester or epoxyresins such as condensation 0.1 m2 percent by weight an aminoalkylalkoxy silane represented by the following structural formula:

wherein R is selected from the group consisting of hydrogen, alkylandH[NHCH CH x being a whole numpolymers of an epihalohydrin and apolyhydroxy phenolic 7 compound and derivatives thereof such asbis-phenol A. Woven roving as described above is saturated with theepoxy resin and meta phenylene diamine. The combination is curedaccording to conventional epoxy resin curing techniques at an elevatedtemperature and pressure.

Itwas particularly noted in the preparation of resinous I laminatesutilizing glass fiber strand treated with a size containing both analkenyl acyloxy silane and an aminoalkyl alkoxy silane according to thepresent invention, that the strands in their various fabricated form,such as cloth, chopped strand mat and woven roving have super-iorwet-out properties as compared to when either of these silanes are usedalone in a size in comparable amounts.

Although the present invention has been described with respect tospecific details of certain embodiments thereof, it is not intended thatsuch details act as limitations upon the scope of the invention exceptinsofar as set forthin' the accompanying claims.

I claim: Y

1. A method of forming-a glass fiber strand which can be fabricated andlaminatedwith a resin which comprises drawing glass streams throughorifices in a bushing to form individual glass filaments, movingthefilaments away from the bushing at a high rate of speed and forming them7 into a strand, applying to the filaments while they are moving at thisspeed an aqueous sizing solutionconsisting essentially of 1 to 5 percentby weight on a solids basis of a synthetic polymer latex of an ethylenicmonomer, 0.3 to 2 percent by weight of an alkenyl acyloxy silane havingthe following structural formula:

her from 1 to 5, R ,is selected from the group consisting of hydrogenand alkyl, R and R are alkyl and n is a whole number from 1 to 3, and0.1 to,1 percent by weight of a textile softener, the total solidscontent of the solution being 2 to 5.5"percent by weight and theviscosity of the solution being less than 100 centipoises at 20 C., anddrying the glass fibers so treated.

2. The method of claim 1 wherein the alkenyl acyloxy silane isvinyltriacetoxy silane.

3. The method of 'claim 1 wherein the aminoalkyl 'alkoxy silane isgamma-amino-propyl triethoxy silane.

4. The method of claim 3 wherein the alkenyl acyloxy silane isvinyltriacetoxy silane.

r 5. The method of claim 1 wherein 0.3 to 2 percent by weight ofmelamine formaldehyde resin is present in the sizing solution.

6. Glass fiber strands formed according to the metho of claim 1.

7. Glass fiber strands formed according to the method ofclaim 2.

' 8. Glass fiber strands formed according to the method of claim 3. n

9. Glass fiber strands formed according to the meth of claim 4. V v w 110. Glass fiber strands formed according to the method of claim ,5.

11. A method of forming a glass fiber, reinforced resinous body whichcomprises forming glass fiber strands bydrawing themfrom molten glassthrough orifices in a bushing to form individual glass filaments, movingthe filaments away fromthe bushing at a high rate of speed and formingthe filaments into a strand, applying to the strands during theirformation while: they are moving at this speed an aqueous sizingsolution which consists essentially of l to 5 percent by weight on asolids basis of a syntheticpolymer latex of an ethylenic monomer, 0.3 toi 2 percent by weight of vinyltriacetoxysilane, 0.1 to 2 percent by'weight of gamma-amino-propyl triethoxysilane and 0.1 to 1 percent byweight of a textile softener, the total solids content of thesolutionbeing 2 to 5.5 percent by weight and the viscosity of the solution beingless than 100 centipoises at 20 C., drying the treated strands,fabricating the glass fiber strands into a form suitable for combiningwith a resin, combining the fabricated strands with a curable resin andcuring -the resin to form the reinforced body.

12. The method described in claim 11 wherein the sizing solutioncontains 0.3 to 2 percent by weight of melamine formaldehyde.

13. An aqueous size for application to glass fiber strands during theirformat-ion which consists essentially a of lto 5 percent by weight on asolids basis of a synthetic polymer latex of an ethylenic monomer, 0.3to 2 percent by weight of an alkenyl acyloxy silane having the followingstructural formula:

wherein R is an. alkenyl radical selected from the group consisting ofvinyl and allyl radicals, R is selected from the group consisting ofhydrogen and an alkyl radical and n is a whole number from 1 to 3, anddissolved therein represented by the following structural formula:

wherein R is selected from the group consisting of hydrogen, alkyl andH[NHCH CH x being a whole number from 1 to 5, R is selected from thegroup consisting of hydrogen and alkyl, R and R are alkyl and n is awhole number from 1 to 3, and 0.1 to 1 percent by Weight of a textilesoftener, the total'solids content of the solu- 0.1 to 2 percent byweight an amino-alkyl alkoxy silane tion being 2 to 5.5 percent byweight and the viscosity of the solution being less than IOO'centipoisesat 20 C.

References Cited in the file oi this patent UNITED STATES PATENTSSteinman 'Aug. 31, 1954 'Brooks July '10, 1956 Werner et a1. NOV."19,1957 Jex et a1. Apr. 29,1958 Hoffman et a1. Apr. 26, 1960 EilermanAugIl, 1961 Jex et al. July 17, 1962

1. A METHOD OF FORMING A GLASS FIBER STRAND WHICH CAN BE FABRICATED ANDLAMINATED WITH A RESIN WHICH COMPRISES DRAWING GLASS STREAMS THROUGHORIFICES IN A BUSHING TO FORM INDIVIDUAL GLASS FILAMENTS, MOVING THEFILAMENTS AWAY FROM THE BUSHING AT A HIGH RATE OF SPEED AND FORMING THEMINTO A STRAND, APPLYING TO THE FILAMENTS WHILE THEY ARE MOVING AT THISSPEED AN AQUEOUS SIZING SOLUTION CONSISTING ESSENTIALLY OF 1 TO 5PERCENT BY WEIGHT ON A SOLIDS BASIS OF A SYNTHETIC POLYMER LATEX OF ANETHYLENIC MONOMER, 0.3 TO 2 PERCENT BY WEIGHT OF AN ALKENYL ACYLOXYSILANE HAVING THE FOLLOWING STRUCTURAL FORMULA: